//===----------------------------------------------------------------------===//
//
// This pass is used to ensure that functions have at most one return and one
-// unwind instruction in them. Additionally, it keeps track of which node is
-// the new exit node of the CFG. If there are no return or unwind instructions
-// in the function, the getReturnBlock/getUnwindBlock methods will return a null
-// pointer.
+// unreachable instruction in them.
//
//===----------------------------------------------------------------------===//
class BasicBlock;
struct UnifyFunctionExitNodes : public FunctionPass {
- BasicBlock *ReturnBlock = nullptr;
- BasicBlock *UnwindBlock = nullptr;
- BasicBlock *UnreachableBlock;
-
public:
static char ID; // Pass identification, replacement for typeid
UnifyFunctionExitNodes();
// We can preserve non-critical-edgeness when we unify function exit nodes
void getAnalysisUsage(AnalysisUsage &AU) const override;
- // getReturn|Unwind|UnreachableBlock - Return the new single (or nonexistent)
- // return, unwind, or unreachable basic blocks in the CFG.
- //
- BasicBlock *getReturnBlock() const { return ReturnBlock; }
- BasicBlock *getUnwindBlock() const { return UnwindBlock; }
- BasicBlock *getUnreachableBlock() const { return UnreachableBlock; }
-
bool runOnFunction(Function &F) override;
};
//
//===----------------------------------------------------------------------===//
//
-// This pass is used to ensure that functions have at most one return
-// instruction in them. Additionally, it keeps track of which node is the new
-// exit node of the CFG. If there are no exit nodes in the CFG, the getExitNode
-// method will return a null pointer.
+// This pass is used to ensure that functions have at most one return and one
+// unreachable instruction in them.
//
//===----------------------------------------------------------------------===//
UnreachableBlocks.push_back(&I);
// Then unreachable blocks.
- if (UnreachableBlocks.empty()) {
- UnreachableBlock = nullptr;
- } else if (UnreachableBlocks.size() == 1) {
- UnreachableBlock = UnreachableBlocks.front();
- } else {
- UnreachableBlock = BasicBlock::Create(F.getContext(),
+ if (UnreachableBlocks.size() > 1) {
+ BasicBlock *UnreachableBlock = BasicBlock::Create(F.getContext(),
"UnifiedUnreachableBlock", &F);
new UnreachableInst(F.getContext(), UnreachableBlock);
}
}
- // Now handle return blocks.
- if (ReturningBlocks.empty()) {
- ReturnBlock = nullptr;
- return false; // No blocks return
- } else if (ReturningBlocks.size() == 1) {
- ReturnBlock = ReturningBlocks.front(); // Already has a single return block
+ // There is nothing more to do if we do not have multiple return blocks.
+ if (ReturningBlocks.size() <= 1)
return false;
- }
// Otherwise, we need to insert a new basic block into the function, add a PHI
// nodes (if the function returns values), and convert all of the return
BB->getInstList().pop_back(); // Remove the return insn
BranchInst::Create(NewRetBlock, BB);
}
- ReturnBlock = NewRetBlock;
return true;
}